This invention relates to a process for producing 5,6-unsubstituted-1,3-dioxin-4-one derivatives.
These derivatives are useful compounds as one of starting raw materials for prostaglandins which are physiologically active substances having various pharmacological activities such as blood pressure depression, anti-ulceration, bronchodilation, inhibition of gastric acid secretion, induction of partus, etc.
The derivatives have not heretofore been known at all, but for the first time the present inventors have found a process for producing 2,2-dimethyl-1,3-dioxin-4-one as a compound belonging thereto. Namely, according to the process reported by the present inventors in Chem. Pharm. Bull. 31, (6) 1896 (1983), 2,2-dimethyl-1,3-dioxin-4-one was obtained from formyl Meldrum's acid in the presence of acetone and using a small amount of toluene or xylene as solvent, with a yield of 31%. This formyl Meldrum's acid seems to have a higher reactivity than that of similar acetyl Meldrum's acid. That is, in the case of the latter acid, its thermal decomposition yielded 2,2,6-trimethyl-1,3-dioxin-4-one, whereas in the case of the former acid, its mere heating in the absence of solvent formed only a resinous substance without yielding 2,2-dimethyl-1,3-dioxin-4-one, but when the former acid was heated in a xylene solvent containing acetone, the compound was obtained for the first time. However, its yield was not only low (yield: 31% as described above), but the loss of the raw material acid due to the resin formation was so great that the recovery of the raw material was impossible.